Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

182
FXUS63 KLOT 111120
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
620 AM CDT Mon May 11 2026

.KEY MESSAGES...

- Briefly warmer (70s) and windy on Tuesday with the potential
  for showers and storms.

- Otherwise cooler (60s) and dry conditions are favored through
  Thursday before a warm-up commences heading into the weekend
  with additional shower/storm chances.

&&

.DISCUSSION...
Issued at 313 AM CDT Mon May 11 2026

Surface high pressure will becoming centered over Lake Michigan
today. The net result being a steady feed of cool onshore
northeasterly flow into our area through the day. Accordingly,
another seasonably cool day is expected, with the coolest
conditions (upper 40s to low 50s) expected along the southern
Lake Michigan shore. Ares farther inland will be a bit warmer,
with upper 50s to low 60s looking to be the general theme across
much of northern IL, though some areas well inland and south of
I-80 could warm a bit more (into the mid to upper 60s) under
mostly sunny skies.

Mainly clear skies, light winds and low surface dewpoints ( in
the upper 20s to around 30) tonight should then support
efficient radiation cooling after sunset, with main locations
outside urban areas of Chicago dropping into the upper 30s to
low 40s overnight. This may thus promote some patchy frost
development late tonight, particularly across far northeastern
IL and northwestern IN where temperatures could briefly fall
below 38 degrees late tonight. Currently, the coverage of frost
looks too low to support the need for a frost advisory.
Nevertheless, anyone with sensitive outdoor vegetation in these
areas should plan accordingly.

The primary forecast attention through the period will be
focused on our next weather maker, which is set to evolve out of
the impulse traversing the Canadian Rockies atop the
southwestern CONUS upper ridge axis today. Ensemble guidance
continues to favor this impulse, along with an associated
surface low, diving southeastward along the northeastern
periphery of the southwestern ridge. This would generally result
in a southeasterly track right across the Upper Midwest late
tonight, then into the western Great Lakes region on Tuesday. A
strong southerly mass wind response in advance of this system
will result in winds across our area quickly turning back to the
south-southwest and increasing in magnitude during the day
Tuesday. Accordingly, this is expected to result in a rather
windy day in our area Tuesday, albeit a warmer one. Model
soundings are ubiquitous in indicating diurnal mixing into 40+
kt flow just a few thousand feet above the surface during the
afternoon, which could certainly support surface gusts topping
35-40 mph.

In addition to the windy conditions on Tuesday, we also
continue to monitor the potential for showers and storms,
particularly in the afternoon and evening. Warm advection on the
strong southwest winds will drive temperatures back into the
70s during the afternoon in advance of an approaching cold
front. However, low-level moisture return on these winds looks
to remain modest, owing to surface high pressure ridging across
the southern states blocking the better Gulf moisture.
Accordingly, this adds questions as to the extent of airmass
destabilization that take place in advance of the front Tuesday
afternoon, particularly considering there may also be some warm
air advection driven mid-level cloud cover and showers shifting
across northern IL during the late morning into the afternoon.
Nevertheless, the presence of strong deep layer flow suggests
that if the warm sector airmass is able to destabilize just
ahead of the front as a result of potential better moisture
pooling, conditions would be supportive of organized isolated
strong convection during the afternoon and evening. This
potential on Tuesday is highlighted by the SPC as a level 1 of 5
severe weather threat.

Temperatures briefly cool down again following Tuesday evenings
cold frontal passage. Breezy northerly winds setting up in its
wake into the day Wednesday will keep high temperatures in the
low to mid 60s. Temperatures then will be on a gradually warming
trend through the end of the week as upper-level ridging builds
across the central CONUS and into the Upper Midwest by the
weekend. The degree of warmth continues to remain in question
given the potential for a period of more active weather later in
the week possibly moderating things a bit. Blended guidance has
accordingly trended a bit cooler with the latest update, with
forecast highs in the mid 70s to lower 80s over the weekend.

KJB

&&

.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 620 AM CDT Mon May 11 2026

VFR conditions with passing mid to upper-level clouds will
persist through the period. NE winds of 10 to 15 knots with
sporadic gusts to 20 knots are expected today. Expect ENE/E
winds under 10 knots this evening to gradually increase to
around 10 knots while veering S by sunrise Tuesday. Winds will
then quickly increase and veer SSW with gusts to 25 knots
Tuesday morning. Beyond the TAF period Tuesday afternoon, SW
winds will gust over 30 knots with a potential for scattered
showers and a few TS late in the afternoon.

Kluber

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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